Robot movement control device and movement control method

ABSTRACT

The present invention corrects a teaching point set in a robot movement control program to another position using jog-feed buttons. A robot tool is moved by jog-feed buttons using a jog-feed command unit toward a position to which a teaching point is to be corrected. When the position of the tool approaches any teaching point contained in a movement command program, the robot is automatically shifted to the teaching point to be corrected in the movement command program. When the teaching point to be corrected is found, correction of a teaching point from the closest teaching point to the position to be corrected is then performed.

TECHNICAL FIELD

This invention relates to a robot movement control device and a robotmovement control method to correct a teaching point set in a program toanother position according to the movement of a tool.

BACKGROUND ART

In conventional control of an industrial robot, an operator teaches atarget point for the movement of a tool attached to the end of a robotarm, and a robot is moved according to a program generated so that therobot reaches this teaching point. Such a teaching point specified bythe program is sometimes deviated from a set point as the result ofvarying the position or direction of a workpiece during work. In thiscase, it is necessary to correct the teaching point deviated from theset point, as a matter of course.

When correction of a teaching point is performed in conventional robotcontrol device, a command block of the teaching point is specified onthe screen of a teaching pendant, and the robot is moved to thespecified teaching point, and is further moved by jog-feed from thespecified teaching point to a corrected teaching point. When the robotreaches the corrected teaching point, a coordinate point of the commandblock is automatically corrected by instructing correction on theteaching pendant.

However, the conventional robot control device described above needs tofind the correspondence between a teaching point to be corrected and itscommand block. Even if this correspondence is found, it is necessary toalternate execution of a program and jog-feed operation with each other,and as a result, working efficiency is degraded.

DISCLOSURE OF THE INVENTION

It is an object of the present invention to provide a robot movementcontrol device and a robot movement control method, which enablecorrection of a teaching point easily with accuracy.

In order to attain the above object, as one mode of a robot movementcontrol device according to the present invention, there is provided arobot movement control device which moves a robot tool to apredetermined teaching point and comprises a program storage unit forstoring a program to instruct the robot to be moved to the predeterminedteaching point, a jog-feed command unit for instructing the robot to bemoved by the jog-feed, a jog-feed control unit for moving the robot bythe jog-feed in the direction instructed by the jog-feed command unit,and a teaching-point directional movement control unit for watching theposition of the robot moved by the jog-feed, and instructing thejog-feed control unit to shift the robot to a teaching point to whichthe robot comes closer, when the robot approaches any teaching point inthe movement command program.

Preferably, the teaching-point directional movement control unit isconfigured to shift the robot tool after the tool is reoriented to aposture instructed by the program.

As another mode of the robot movement control device according to thepresent invention, there is provided a robot movement control devicewhich moves a tool of a robot to a predetermined teaching point andcomprises a program storage unit for storing a program to instruct therobot to be moved to the predetermined teaching point, a jog-feedcommand unit for instructing the robot to be moved by the jog-feed, ajog-feed control unit for moving the robot by the jog-feed in thedirection instructed by the jog-feed command unit a shifting commandunit for instructing the robot to be shifted to a predetermined teachingpoint, and a teaching-point directional movement control unit forinstructing the jog-feed control unit to shift the robot to a teachingpoint, which is the closest to the position of the robot among teachingpoints in the movement command program, when the instruction to shiftthe robot is performed.

Further, in a robot movement control method according to the presentinvention, a teaching-point move mode is set in a control device forcontrolling a robot. When the control device enters this teaching-pointmove mode by switching operation to move a tool attached to the end of arobot arm by the jog-feed toward a target position to which the teachingpoint is to be corrected a numerical control unit decides during thejog-feed as to whether or not the current position of the tool is withinthe range of a predetermined distance from a programmed teaching point.When decided that the current position of the tool is within thepredetermined range, the tool is forcibly shifted to the programmedteaching point, and is positioned at the target teaching point to becorrected. Further, when the current position of the tool is within thepredetermined range of the programmed teaching point, the tool isshifted to the teaching point after the tool is reoriented to thedirection taught in the programmed teaching point.

According to the present invention, first, the tool is moved in thedirection commanded by the jog-feed command means. When the toolapproaches any teaching point in the movement command program, the robotis operated to shift the tool to the teaching point. As a result, anoperator is able to judge a position, in which the robot is stopped, tobe one of teaching points in the movement command program. Further, ifthe tool is fed by jog-feed from this teaching point to a position to beset as a new teaching point, it is possible to correct a teaching pointfrom a programmed teaching point to a target point for the movement ofthe tool.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a conceptual view for explaining the function of oneembodiment according to the present invention;

FIG. 2 is a view showing the overall configuration of a robot controlsystem including a robot movement control device according to theembodiment;

FIG. 3 is a block diagram showing the hardware configuration of a robotcontrol device;

FIG. 4 is a view showing the schematic configuration of a panel face ofa teaching pendant;

FIG. 5 is a view showing the operation of a tool of a robot; and

FIG. 6 is a flowchart showing a procedure on the side of a robot controldevice for controlling the movement of a robot according to theembodiment.

BEST MODE FOR EMBODYING THE INVENTION

First of all, a description will be given of the outline of a functionaccording to an embodiment of the present invention with reference toFIG. 1. A program 1a to instruct a robot to be moved to a predeterminedteaching point is stored in a program storage unit 1. A jog-feed controlunit 3 moves a robot by jog-feed in the direction instructed by ajog-feed command unit 2. For instance, the jog-feed control unit 3 movesa tool 4a along a jog command route L11. A teaching-point directionalmovement control unit 5 watches the position of a robot 4 moved byjog-feed, and instructs jog-feed control unit 3, when the tool 4a (thatis, a tool center point) of the robot 4 approaches any teaching pointPx, to shift the tool 4a of the robot 4 to the teaching point Px in themovement command program 1a. As a result, the tool 4a goes out of thejog-command route L11 and is shifted toward the teaching point Px alonga route L12.

A description will now be given of the overall configuration of a robotcontrol system for embodying a robot movement control device as oneembodiment of the present invention with reference to FIG. 2. A tool 12is attached to the end of an arm 11 of a robot 10. The robot 10 isadapted to machine or carry a workpiece 20, and its operation iscontrolled by a robot control device 30. The operation of the robot 10is instructed by a teaching pendant 40 connected to the robot controldevice 30. The teaching pendant 40 has such a size as to make handy foran operator to carry. The teaching pendant 40 includes a liquid crystaldisplay panel and various keys as will be described later.

FIG. 3 is a block diagram showing the hardware configuration of therobot control device 30. The robot control device 30 includes aprocessor board 31. This processor board 31 includes a processor 31a,ROM 31b and RAM 31c. The processor 31a controls the entire robot controldevice 30 according to a system program stored in ROM 31b. Various datasuch as a movement command program of the robot 10 are stored in RAM31c. Coordinates of a teaching point and the direction (i.e.,coordinates of an axis of rotation) of the tool 12 are stored in eachcommand block of the movement command program. Such a processor board 31is connected to a bus 39.

A digital servo control circuit 32 is connected to the bus 39, anddrives servo motors 51, 52, 53, 54, 55 and 56 through a servo amplifier33 according to the command from the processor board 31. These servomotors are built in the robot 10 and operate each axis of the robot 10.

A serial port 34 is connected to the bus 39, and also connected to boththe teaching pendant 40 with a display and other RS232C apparatus 58.The teaching pendant 40 has a size to make handy for an operator tocarry, as described above, and is provided with a jog-feed button and ateaching point correction button or the like on the panel. CRT display36a may be optionally connected to the serial port, and it is possibleto check the working state or the like on the CRT display 36a.

A console panel 36b is connected to a digital I/O unit 35, and themovement of the robot 10 may be instructed at the position of the robotcontrol device 30 through the teaching pendant. A drive portion to gripthe tool 12 is connected to the digital I/O unit 35 which is able toinstruct the gripping operation. When a machining head for laser weldingis used for the tool 12, for instance, a welding power supply isconnected to an analog I/O unit 37, and a welding voltage is instructedthrough the analog I/O unit 37. Teaching data and others are stored in amass memory 38.

FIG. 4 is a view showing the schematic configuration of a panel face ofthe teaching pendant 40. A display screen 41 is a liquid crystal screen,for instance, and detailed data or similar data in the movement commandprogram is selectively displayed by switching. A function key 42 is akey which selects a menu displayed on the lower end of the displayscreen 41. This function key 42 also serves to perform switching to ateaching-point move mode and to instruct a correction of a teachingpoint. A teaching pendant valid switch 43 is a switch which makes the ofthe teaching pendant 40 invalid from valid and vice versa.

An emergency stop button 44 is a button which stops the operation of therobot 10 in an emergency. A cursor key 45 is a key which moves a cursordisplayed on the display screen 41. A ten-key pad 46 includes numericalkeys and other keys which enable the input and deletion of numericalvalues and characters.

A jog-feed command unit includes a shift button 48 and jog-feed buttons47. First, either an orthogonal coordinate system (X, Y, Z) or eachjoint axis (J1 to J6) is selected by depressing a coordinate selectionbutton 49. In case where the orthogonal coordinate system is selected,if any one of the jog-feed 47 buttons indicating plus or minus lineardirection for each of X, Y and Z axis is selectively depressed togetherwith the shift button 48, then the robot is moved by jog-feed in theselected direction for the selected axis. On the other hand, if any oneof the jog-feed buttons 47 indicating plus or minus rotational directionabout each of X, Y and Z axis is selectively depressed together with theshift button 48, then the robot is moved by jog-feed in the selectedrotational direction about a selected axis. Further, in case whereindividual joint-axis feed mode comes into effect by depressing thecoordinating selection button 49, if any one of the jog-feed buttons 47for each joint axis (J1 to J6) is selectively depressed, then jog-feedof the robot for the selected joint axis is carried out.

A description will now be given of the specific processing contents ofthe robot movement control device as one embodiment of the presentinvention.

FIG. 5 is a view showing the operation of the tool 12 of the robot 10.In this case, a workpiece 20 is a thin sheet, and the robot performs theoperation of gripping this thin sheet (i.e., workpiece 20 ). A point Ptof the workpiece 20 is assumed to be a teaching point predetermined inthe movement command program. A description will now be given of a casewhere an attempt to shift the tool 12 to a point Pa is made in orderthat the point Pa close to the teaching point Pt is set as a newteaching point in place of the point Pt.

First, an operator depresses the jog-feed button 47 on the teachingpendant 40 to shift the tool 12 (i.e., a tool center point) toward thetarget point Pa (along the route L1). During the movement of the tool12, the teachingpoint directional movement control unit 5 watches at alltimes the position of the tool moved by the jog-feed. When the tool 12enters the range of a predetermined radius from the teaching point Ptduring the shifting of the tool 12 toward the point Pa, theteaching-point directional movement control unit 5 detects the approachof the tool 12. In this case, "the range of a predetermined radius" unita distance set to be shorter to some extent than the distance betweenthis point Pa and any other teaching point.

The teaching-point directional movement control unit 5 reorients thetool 12, at the detected position Pc, so that its direction is same asthe direction specified in the teaching point Pt. Then this reorientedtool 12 is shifted toward the teaching point Pt along the differenttrack (along the route L2). When the tool 12 reaches the teaching pointPt, the tool 12 is stopped. When the tool center point of the tool 12 isstopped at the teaching point Pt, the correction of the teaching pointis performed according to a method similar to the conventional method.That is, the operator depresses the jog-feed button 47 to shift the toolto the target point Pa. When the tool reaches the point Pa, thecorrection of the teaching point is instructed by depressing thefunction key 42 or the like. As a result, rewrite from the coordinatedata of the teaching point Pt to the coordinate data of the point Pa isperformed on the side of the robot control device 30.

A description will now be given of the procedure in case where theprocessor 31a of the robot control device 30 performs the aboveoperation with reference to the flowchart shown in FIG. 6.

The function key 42 is depressed to switch a mode to the teaching-pointmove mode, and the jog-feed button 47 is depressed to start a shiftingcontrol so as to shift a teaching point toward a position to becorrected (Step S1). An axis is controlled according to the selectedcoordinate system and the axis and its direction corresponding to thedepressed jog-feed button 47, and the jog-feed of the tool 12 is started(Step S2). It is decided as to whether or not the jog-feed command is inthe off state (Step S3). When the jog-feed command is not in the offstate, it is decided as to whether or not the teaching-point move modeis selected (Step S4). When the teaching-point move mode is notselected, processing is returned to Step S3. On the other hand, when theteaching-point move mode is selected, it is decided as to whether or notthe position of the jog-fed tool 12 is within the range of apredetermined radius (i.e., within the predetermined distance) from anyteaching point in the movement command program (Step S5). When decidedthat the position of the tool 12 is outside the range of thepredetermined distance, processing is returned to Step S3. On the otherhand, when decided that the position of the tool 12 is within the rangeof the predetermined distance, then it is decided as to whether or notthe tool 12 approaches the teaching point (Step S6). When decided thatthe tool approaches the teaching point, processing is advanced to StepS7. On the other hand, when decided that the tool is moved away from theteaching point, processing is returned to Step S3.

That is, while the jog-feed command is in the on state, processing inSteps S3 to S5 is repeatedly executed. When the distance between thecurrent position of the tool 12 and the teaching point is within thepredetermined range (Step S5), it is decided as to whether or not thetool approaches the teaching point by the jog-feed (Step S6). Whendecided that the tool approaches the teaching point by the jog-feed,processing is advanced to Step S7. In Step S7, the tool 12 isautomatically reoriented to the direction as it is programmed in theabove teaching point. Further, it is decided as to whether or not thejog-feed command is in the off state (Step S8). When decided that thejog-feed command is not in the off state, then it is decided as towhether or not the tool 12 is completely reoriented (Step S9).Processing in Steps S8 and S9 is repeatedly executed until the tool 12is completely reoriented.

After the tool 12 is completely reoriented, the shifting of the tool 12toward the teaching point Pt is automatically started (Step S10). Then,it is repeatedly decided as to whether or not the jog-feed command is inthe off state, and whether or not the tool 12 reaches the targetteaching point Pt when decided that the jog-feed command is not in theoff state (Steps S11 and 12). When the tool 12 reaches the targetteaching point Pt, the robot is stopped even if the jog-feed command isin the on state (Step S13). In this manner, when the operation of therobot is stopped even if the jog-feed command is in the on state, thetool 12 is regarded as having reached the teaching point. Therefore, thecorrection of the teaching point is afterward performed according to thesame method as the conventional method.

Incidentally, when the robot 10 is stopped before the tool 12 exactlyreaches its desired teaching point (i.e., when the tool is stopped at awrong teaching point), the jog-feed command is set to the on state tomove the tool 12 away from the teaching point. As a result, processingin Steps S1 to S6 is executed. In this case, since the tool does notapproach the teaching point in Step S6, processing is returned to Step3, and the tool 12 is moved away from the teaching point in the samecondition. Then, the tool is moved by jog-feed toward the desiredteaching point, and processing in Steps S1 to S13 is executed toposition the tool 12 at the desired teaching point. When the jog-feedcommand is set to the off state in Steps S3, S8 and S11 before the tool12 reaches the teaching point, the movement of the robot is stopped.However, in this case, when the jog-feed command enters again,processing in Steps S1 to S13 is executed, and therefore, the tool isable to be moved to and stopped at the desired teaching point.

As described above, according to the present invention, when a toolapproaches a teaching point set in advance in the movement commandprogram while moving by jog-feed toward a point to be set as a newteaching point, the tool is automatically shifted to the predeterminedteaching point. Therefore, an operator is able to recognize that theposition where the robot 10 is stopped is a teaching point in themovement command program. Further, if the tool is moved by jog-feed fromthat position to a target position (i.e., a point to be set as a newteaching point) according to the conventional operation, it is possibleto perform the correction of a teaching point. Therefore, time requiredfor work is reduced.

Further, according to the embodiment of the present invention, when themovement according to the jog-feed command inputted by the operator ischanged to the automatic shifting to a teaching point, the direction ofthe tool 12 is changed to the same direction as the direction specifiedby the program data of the teaching point before change of the movingdirection. Therefore, it is possible to prevent the tool frominterfering with another part of a workpiece, and work with moreaccuracy is enabled.

According to the embodiment of the present invention, the tool isautomatically shifted toward the teaching point at a point of time whenthe tool approaches the teaching point. However, this shifting may alsobe made according to the operator's specific operation on the teachingpendant 40.

Further, in the embodiment of the present invention, a description hasbeen given of a case where the tool 12 of the robot 10 grips aworkpiece. But, the present invention may be applied to a tool such as awelding head.

We claim:
 1. A robot movement control device for moving a robot tool toa predetermined teaching point, comprising:a program storage means forstoring a program to instruct the robot to be moved to the predeterminedteaching point; a jog-feed command means for instructing the robot to bemoved by the jog-feed; a jog-feed control means for moving said robot bythe jog-feed in the direction instructed by said jog-feed command means;and a teaching-point directional movement control means for monitoring aposition of the robot moved by the jog-feed, determining the teachingpoint located nearest to said position, and instructing said jog-feedcontrol means to shift said robot, when it approaches any teaching pointin the movement command program, to said teaching point located nearestto said position.
 2. A robot movement control device according to claim1, wherein said teaching-point directional movement control means shiftssaid robot tool after said tool is reoriented to a posture instructed bysaid program.
 3. A robot movement control device for moving a robot toolto a teaching point given in advance, comprising:a program storage meansfor storing a program to instruct the robot to be moved to thepredetermined teaching point; a jog-feed command means for instructingthe robot to be moved by the jog-feed; a jog-feed control means formoving said robot by the jog-feed in the direction instruction by saidjog-feed command means; a shifting command means for instructing therobot to be shifted to a teaching point given in advance; and ateaching-point directional movement control means for instructing saidjog-feed control means to shift said robot to a teaching point which isthe closest to a position of said robot among the teaching points insaid movement command program, when said instruction to shift the robotis performed.
 4. A method of robot movement control which moves a robottool to a predetermined teaching point, comprising the steps of:storingthe robot movement command program having a plurality of teachingspoints used to instruct the robot to move along a path; moving the robotto a position through the use of jog-feed buttons; monitoring andstoring said position of the robot moved by the jog-feed buttons;determining which teaching point stored in the program having aplurality of teaching points is located nearest to said position; movingsaid robot in accordance with said movement command program; andshifting the movement of said robot to said position, when the robotapproaches said teaching point located nearest to said position.
 5. Amethod of robot movement control as recited in claim 4, wherein saiddetermining step determines which teaching point is located nearest tosaid position using a minimum predetermined distance.
 6. A method ofrobot movement control which corrects a teaching point set in a robotmovement command program by moving a robot tool to a predeterminedteaching point, comprising the steps of:storing the robot movementcommand program having a plurality of teachings points used to instructthe robot to move along a path; moving the robot to a position throughthe use of jog-feed buttons; monitoring and storing said position of therobot moved by the jog-feed buttons; executing said robot movementcontrol program; moving said robot in accordance with said movementcommand program being executed; and shifting the movement of said robotto said position, when the robot approaches a teaching point that iswithin a predetermined distance to said position.